Structural effects of Zn²⁺ on cell membranes and molecular models

Zinc is an essential element for nutrition as well as for the proper development and function of brain cells, and its traces are present in a wide range of foods. It is a constituent of many enzyme systems and is an integral part of insulin and of the active site of intracellular enzymes. However, excessive accumulation of zinc or its release from the binding sites may become detrimental for neurons. With the aim to better understand the molecular mechanisms of the interaction of zinc ions with cell membranes, it was incubated with intact human erythrocytes, isolated unsealed human erythrocyte membranes (IUM), cholinergic murine neuroblastoma cells, and molecular models of cell membranes. These consisted in bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), phospholipid classes present in the outer and inner monolayers of most plasmatic cell membranes, particularly that of human erythrocytes, respectively. The capacity of zinc ions to perturb the bilayer structures of DMPC and DMPE was assessed by X-ray diffraction, DMPC large unilamellar vesicles (LUV) and IUM were studied by fluorescence spectroscopy, intact human erythrocytes were observed with scanning electron microscopy (SEM), and neuroblastoma cell morphology was observed under inverted microscope. This study presents evidence that 0.1 mM Zn and higher concentrations affect cell membrane and molecular models.